why is my front brake so soft?

[Guest]

As i posted in a different thread i switched my forks from L forks back to factory G's. While doing this i needed to swap the master cylinder out due to a lot of play in the lever (up and down not forward and back). I switched master cylinders and bled the brakes. The handle was pretty soft but I took it down the road and it stops but just not the way it used to. I got a vacuum bleeding kit and bled the brakes with it to no luck i went ahead and basically drained out the old fluid and put in new fresh fluid. The handle was a little better but was still not firm as in it can touch the grip with the lever. Fast forward to today, I switched master cylinders again bled the brakes again, mind you I've went through a large container and flushed and flushed and flushed. I did switch to a 1/2' Nissin for the second front master cylinder i realize this will give me a softer front lever but it also can be pulled to touch the grips. i flushed and flushed again, then i took a syringe and flushed back through the bleeder to no avail. I then took the calipers apart to clean and service but they are super clean there were no blemishes, scraped gunk,or any of the typical dirt issues. I'm out of ideas,
here is what i have done
1. fluid is clean
2. bled bled bled
3. cleaned calipers,
4. changed master cylinders again
5. quit and I'm now drinking beer

Thanks for looking-James

[fastbysuzuki]

If the master cylinder with up and down play in the lever was ok could you not just shim out the play?
not really sure where you are at regarding swapping the master Cyinders using different bore sizes will give different results.
there are a number of reasons if the lever comes back to the bars.
1 air in the system
2 master cylinder not pushing enough fluid through to push the caliper Pistons far enough out to contact the pads to the rotor/rotors with 1 pull of the lever.
3 old rubber brake lines swelling when pressure is applied.
4 leaks
what happens when you pump the lever back/forward fast does the lever still go back to the bars?

[Nessism]

You need a 5/8" master. The 1/2" master will feel spongy at the lever no matter what. I'd change to the proper size and replace the brake lines to teflon/stainless type.

As a bandaid fix you might want to try pumping up the hand lever and then tieing the handle back against the grip with as much pressure in the system as possible. Often times when working on your brakes the pistons sit away from the disc and don't move close enough. Tieing back the lever will often allow the pistons to slowly creep closer to the disc and firm up the lever. If you used K&L brake system caliper seals that's a red flag too since they don't fit right and can cause this same issue. I learned this the hard way.

[Gs1000g]

Hey. The master cylinder I replaced would "bind up" that's what I'm calling it, sometimes giving a little pressure it would catch the top or bottom and drag, the last time it did it I was entering a curve and I wanted a little brake well I ended up with a whole lot and I did not like that, I also had already put a shim in it to help and made sure there were no burs to make it bind up. it also was not the piston but the actual handle and housing component. the seals are OEM, the calipers were really clean actually when disassembled.

[fastbysuzuki]

You did not mention that the master cylinder that was fitted was binding up.
you have also not said how old your brake lines are?
in fairness the advice you have been given by all will fix the problem.

[Gs1000g]

You did not mention that the master cylinder that was fitted was binding up.
you have also not said how old your brake lines are?
in fairness the advice you have been given by all will fix the problem.

The actual piston was not binding, it was more the handle against the reservoir/ ears bolt area, there was quite a bit of play up and down in the lever and i tried to tighten more just wouldn't work. I then put a washer in there but it actually made it less predictable than before so I took it out. Anyways, this morning i swapped out the master cylinders for another one, which just didn't work at all it was the master cylinder not anything else. I then replaced it again with another one....which also was a soft one, so i went and took one off another parts bike this one fixed it. I don't know what the problem was except all 3 master cylinders wouldn't work but this one fixed it. its the proper 5/8 piston as were the other two. In a moment of anger last night I ordered a new set of stainless steel brake lines that should be here in maybe a week or so. I don't know the age of the current lines except they were on the bike when I got them. (see i told the wife buying a barn of parts would come in handy eventually)

Thanks for all the replies-James

[Joe Garfield]

I rebuilt my calipers and cleaned my M/C last week, and after a proper brake bleeding still had a spongy lever. I followed the advice squeezing the lever to the handle and tying it there overnight, and it made a huge difference.

[Gs1000g]

I also did this and it does make a huge difference, but my new braided lines are now in so I have to do this all over again ��

[Gs1000g]

Update: bled and bled the brakes new master cylinder helped, last night I installed the new braided brake lines from Apex Brakes and holy **** its a huge difference. This could be the best riding upgrade I have done.
with the proper sonic springs proper G forks, new brakes, new lines. This is a whole different bike and makes it much more nimble and fun to ride.